See MDMA Effects for a more complete list of MDMA's effects, this article
is focused on giving an overview of MDMA's (generally unwanted) side effects profile and is neither a complete
list of possible side effects nor does it represent the full range of effects of MDMA.

Based on reports
from users, common adverse side effects of MDMA ingestion include rise in blood pressure and heart rate, nystagmus (eye-wiggling),
trismus (jaw tension), bruxia (teeth grinding), sweating, agitation, a post-peak crash, muscle
tension, headaches, nausea & vomiting, dry-mouth, liver problems, water retention, fatigue, confusion,
mood swings, black outs, etc. While these effects have been known for years, there hasn't
been much data about the prevalence of these various side effects.

In January 2001, the first peer reviewed paper to have a good overview of the subjective
side effects was published by Liechti, Gamma, and Vollenweider
in the journal Psychopharmacology.
Their paper was based on clinicial research conducted over several years involving 74 healthy volunteers.

The researchers found that there were a number of common side effects and that many
of the effects seemed to occur in different amounts based on gender. The top side effects
reported were Difficulty Concentrating, Jaw Clenching, Lack of Appetite, and Dry Mouth/Thirst
(all occuring in more than 50% of the 74 volunteers).

Liechti et al summarize the adverse effects by saying "Adverse effects were more frequently reported by women compared to men and mainly included jaw clenching or increased tension in maxillary muscles, dry mouth, and lack or loss of appetite. Sweating and nausea were more frequent in men. At the onset of the MDMA effect some subjects reported nausea, hot flushes, paresthesia, and dizziness. Tremor and increased restlessness were observed in about one-third of the subjects. Side effects were generally considered mild and were similar to those reported in previous controlled studies (Vollenweider et al. 1998a) or by Ecstasy users (Peroutka et al. 1988; Solowij et al. 1992). There were no complications requiring medical intervention."

Numbers indicate percentage of all subjects under MDMA reporting
a specific complaint. Numbers in parentheses indicate percentage of all subjects
under placebo reporting a specific complaint.

Acute Adverse EffectsMDMA (Placebo)

After Effects at 24 hrs afterMDMA (Placebo)

Alln=74

Femalen=20

Malen=54

Alln=74

Femalen=20

Malen=54

Difficulty concentrating

59 (15)

75 (15)

54 (15)

28 (8)

30 (10)

28 (7)

Jaw clenching

58 (0)

65 (0)

56 (0)

20 (0)

25 (0)

19 (0)

Lack of appetite

54 (4)

75 (5)

46 (4)

39 (3)

50 (0)

35 (4)

Dry mouth/thirst

53 (3)

65 (5)

48 (2)

34 (4)

60 (10)

24 (2)

Impaired balance

49 (0)

50 (0)

48 (0)

7 (0)

5 (0)

7 (0)

Restless legs

41 (1)

40 (0)

41 (2)

11 (1)

5 (0)

13 (2)

Sensitivity to cold

41 (11)

50 (15)

37 (9)

12 (3)

10 (10)

13 (0)

Dizziness

38 (1)

40 (0)

37 (2)

7 (0)

10 (0)

6 (0)

Palpitations

35 (1)

50 (0)

30 (2)

7 (0)

15 (0)

4 (0)

Restlessness

34 (1)

35 (0)

33 (2)

12 (1)

15 (5)

11 (0)

Being cold

34 (7)

45 (15)

30 (4)

9 (3)

20 (10)

6 (0)

Sweating/sweaty palms

31 (0)

20 (0)

35 (0)

12 (0)

5 (0)

15 (0)

Forgetfulness

28 (1)

40 (5)

24 (0)

11 (1)

10 (0)

11 (2)

Heavy legs

27 (1)

50 (0)

19 (2)

12 (0)

20 (0)

9 (0)

Fatigue

26 (47)

35 (45)

22 (48)

41 (26)

55 (25)

35 (26)

Weakness

26 (1)

35 (5)

22 (0)

24 (1)

35 (5)

20 (0)

Hot flushes

24 (3)

40 (5)

19 (2)

15 (1)

20 (5)

13 (0)

Tremor

23 (0)

25 (0)

22 (0)

8 (0)

10 (0)

7 (0)

Paresthesia

22 (9)

25 (15)

20 (7)

1 (8)

5 (10)

0 (7)

Inner tension

20 (5)

15 (5)

22 (6)

8 (5)

10 (5)

7 (6)

Brooding

16 (3)

20 (0)

15 (4)

18 (1)

20 (0)

17 (2)

Nausea

15 (3)

10 (5)

17 (2)

1 (0)

0 (0)

2 (0)

Lack of energy

15 (8)

25 (10)

11 (7)

24 (4)

40 (5)

19 (4)

Exhaustibility

15 (4)

15 (10)

15 (2)

19 (1)

30 (0)

15 (2)

Frequent urge to urinate

14 (5)

10 (10)

15 (4)

15 (5)

15 (10)

15 (4)

Headache

12 (12)

15 (20)

11 (9)

27 (7)

35 (10)

24 (6)

Insomnia

-

-

-

24 (0)

30 (0)

22 (0)

Anxiety

11 (1)

15 (5)

9 (0)

1 (1)

5 (0)

0 (2)

Irritability

8 (1)

15 (5)

6 (0)

5 (0)

15 (0)

2 (0)

Increased appetite

4 (7)

0 (5)

6 (7)

1 (3)

0 (0)

2 (4)

Muscle aches

1 (3)

5 (5)

0 (2)

3 (3)

5 (0)

2 (4)

Bad dreams

-

-

-

7 (3)

15 (5)

4 (2)

There are also a variety of other less common side effects which have been reported by
users. All psychoactives have a wide variety of idiosyncratic effects and psychedelics
in general can cause nearly any type of symptom to manifest because they affect the
mind, the general nervous-system, regulatory chemical systems, and one's perceptions.
Less common side effects include hyper-salivation (uncontrollable, profuse saliva),
paranoia, a profound sense of isolation & loneliness, psychotic episodes, extreme
panic attacks, extreme depression, and a variety of other more mild mental/spiritual disruptions.

Liechti et al also measured some of the test subjects for blood pressure, heart rate, and
body temperature against a placebo control. The increases were noticeable, but not
dangerous and not statistically significant for many of the readings (this means that
the changes they measured were not certain to be an effect of the drug instead of
random chance).

Liechti summarized the Physiological effects they measured, saying
"MDMA increased heart rate in both genders by 13 beats/min compared
to placebo, however, this was only significant in men. Similarly, peripheral body
temperature was increased significantly by 0.4C compared to placebo in male subjects
while MDMA-induced increases in body temperature did not reach statistical significance
in female subjects. All body temperatures remained below 38C. There were no correlations
between the dose per kilogram body weight and blood pressure or body temperature values."